Steam-engine



(No Model.)

2 Sheets-Sheet 1. M. B. DODGE.

STEAM ENGINE.

No. 450,780. Patented Apr. 21,1891.

(No Model.) 2 Sheets-Sheet 2. M. B. DODGE.

STEAM ENGINE. No. 450,780. Patented Apr. 21,1891.

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NiTEn STATES PATENT OFFICE.

MILES B. DODGE, OF SAN FRANCISCO, CALIFORNIA.

STEAM-ENGINE.`

SPECIFICATION forming part of Letters Patent No. 450,780, dated April21, 1891.

Application led February 18,1890. Serial No. 340,970. (No model.)

To a/ZZ whom, it may concern:

Be it known that I, MILES B.DODGE, acitizen of the United States,residing` in the city and county of San Francisco, State of California,have invented an Improvement in Steam-Engines; and I hereby declare thefollowing to be a full, clear, and exact description of the same.

My invention relates to certain improvements in steam-engi nes.

It consists of a cylinder, a piston reciprocating therein and having theareas of steamspace of different sizes upon the two sides of the piston,a valve by which the steam is transferred from the side of smallest areato the opposite side, so as to act expansivcly therein, and thecombination therewith of a cut-off valve and certain details ofconstruction,all of which will be more fully explained by reference tothe accompanying drawings, in which- Figure 1 is a sectional view of theenginecylinder and valves, showing the piston at the upper end of itsstroke. Fig. 2 shows the piston midway in its descending stroke. Fig. 3shows the pistou at the bottom of the stroke. Fig. 4- shows the pistonmidway of its ascending stroke, the relative positions of the valvesbeing shown in each ease.

A is an engine-cylinder having the piston B reciprocating therein andthe piston-rod C.

Upon the side of the cylinder opposite the piston-rod is acylinder-chamber D, concentric and in line with the main cylinderA, andEis a plunger forming an extension from the piston B and travelingwithin the eXtension D.

F F are packing-rings, which form a tight joint between the plungerE andthe interior of the cylindrical extension D.

G is a valve-chamber having the steam-inlet II.

I is the main valve, which is ot the wellknown D form, but having anextension at one end, with a port J passing through it.

K K are the steam-admission ports leading from the valve-chamber to theopposite ends of the cylinder A, and L is an exhaustport so arrangedwith relation to the lower steam-port K that when the valve I is in theproper position the two ports are connected,

so as to allow the steam to exhaust from the lower part oi the cylinderA through these ports.

Upon the back of the valve I is a cut-off valve M, which is moved by anindependent Valve-stem N, the main valve being moved by the stem O. Thiscut-off valve controls the steam-passage J through the main valve andoperates to close this passage at a certain portion of the stroke of theengine.

The operation of my engine will then beas follows: rIhe piston being atthe top of the cylinder, as represented in Fig. l, the valveI is inposition to admit steam through the ports J and K into the upper part ofthe cylinderA above the pistou B. At the same time the exhaust-port L isin communication with the lower steam-port K through the chamber beneaththe valve I, so that as steam is admitted through the ports J and Kabove the piston B to force the latter down the steam which is beneaththe pistonin the cylinder A will escape through the ports II and L. rlhecut-off valve M is in such position as to expose the port J in the mainvalve and allow steam to pass through it.

In Fig. 2 the piston B is represented as having completed halt of itsdownward stroke. The valve INI has moved so as to cut ott thesteam-passage J through the valve I, andthe steam which is now withinthe cylinder above the piston B must act expansively during theremainder of the downward stroke of the piston. The exhaust-passage isstill open for the escape of steam from below the piston.

In Fig. 3 the piston is represented as having completed its downwardstroke, and the valves are in posit-ion for its return. In this figurethe valve M has moved downward to the lower part of its stroke and thevalve I has moved upward, so as to connect the steampassages K and Ii bymeans of the chamber beneath the valve. The passage J, being upon thevalve-face in the steam-chest, communicates with nothing. Steam is nowallowed to pass through the space above the piston B, through the portsI( and K', into the space below the piston, and this space being of muchlarger area than the space above the piston, this steam which is actedcxpansively above the piston during the latter portion of its downwardstroke, is now allowed to pass bolow the piston and complete itsexpansionin forcing the latter upward to the upper end of its stroke.

Fig. 4E shows the piston midway in its upward stroke. By thisconstruction I am enabled to use the steam at high pressure above thepiston in that portion of the cylinder which has the least area, and fora portion ot the stroke, then complete the downward stroke by theexpansion of this high-pressure steam, and afterward continue the upwardstroke of the piston by the continued expansion ofthis steam, which isadmitted from the upper side of the piston to the lower side. In orderto prevent the piston from striking the bottom of lthe cylinder in itsdownward stroke, I have so proportioned the area of the chamber D abovethe plunger E that the vacuum produced in this space as the plungermoves downward will be sufficient to act as a cushion, the vacuumpreventing the piston from striking the bottom of the cylinder.

P is a small valve at the upper end of the chamber D, which closesinwardly and prevents the entrance of air into the chamber D, but incase of any slight leakage will allow any air or vapor within thechamber to es cape when the plunger E rises.

I have here described my engine as using the ordinary slide-valve andcut-oil; but it will be manifest that other forms of valves may besubstituted for these, which will admit'the steam in the manner hereindescribed.

Having thus described my invention, what I claim as new, and desire tosecure by Letters Patent, is-

A vertical engine consisting of a main steam-cylinder and an extensionof smaller diameter at the top in line therewith, a piston reciprocatingin the main cylinder, a trunk projecting from the upper side of thepiston so as to reciprocate within the extension of the cylinder andproduce a vacuum on its downward stroke, and an outwardlyopeningrelief-valve in said extension, a valve-chamber with steam-supply portsleading to opposite ends of the main-cylinder only, and an exhaust-portoutside of and in line with the steam-ports, a valve having an extensionat one end with a port corresponding with the upper steam-port and aconcavity in its face, which alternately connects the two steam-portsand the lower steam and the exhaust port, and a cut-off valvereciprocating upon the main valve to open and close the single port insaid valve,substantial1y as herein described.

In witness whereof I have hereunto set my hand.

MILES B. DODGE.

W'itnesses:

S. I-I. NoURsE, II. C. LEE.

